A Hardware Abstraction Layer (HAL) for embedded systems
This project is developed and maintained by the HAL team.
At the moment we are working towards a
1.0.0 release (see #177). During this process we will
release alpha versions like
Alpha releases are not guaranteed to be compatible with each other.
They are provided as early previews for community testing and preparation for the final release.
If you use an alpha release, we recommend you choose an exact version specification in your
embedded-hal = "=1.0.0-alpha.2"
See below for a way to implement both an
0.2.x version and an
side by side in a HAL.
How-to: add a new trait
This is the suggested approach to adding a new trait to
Research / Discussion
Ideally, before proposing a new trait, or set of traits, you should check for an existing issue suggesting the need for the trait, as well as any related works / use cases / requirements that are useful to consider in the design of the trait.
These issues will be labeled as
discussion in the issue tracker.
Implementation / Demonstration
Proposed traits should then be implemented and demonstrated, either by forking
embedded-hal or by creating a new crate with the intent of integrating this into
embedded-hal once the traits have stabilized. You may find cargo workspaces and patch useful for the forking approach.
Traits should be demonstrated with at least two implementations on different platforms and one generic driver built on the trait. Where it is possible we suggest an implementation on a microcontroller, and implementation for linux, and a driver (or drivers where requirements are more complex) with bounds using the trait.
Proposing a trait
Once the trait has been demonstrated a PR should be opened to merge the new trait(s) into
embedded-hal. This should include a link to the previous discussion issue.
If there is determined to be more than one alternative then there should be further discussion to
try to single out the best option. Once there is consensus this will be merged into the
These issues / PRs will be labeled as
proposals in the issue tracker.
Implementations and drivers
For a list of
embedded-hal implementations and driver crates check the awesome-embedded-rust
Adding support for an
-alpha version in a HAL implementation
It is possible for HAL implementations to support both the latest
0.2.x version of
as well as the latest
1.0.0-alpha version side by side. This has several big advantadges:
- Allows for a more gradual upgrade process within the community.
- Allows for a faster upgrade to
1.0once it comes out.
- Provides more oportunities to test the new
This approach has been implemented in LPC8xx HAL. Here are the steps:
- Add a dependency to the latest
Cargo.toml. Use the
packageattribute to refer to it by another name, to prevent name collision (example).
- Import the traits into the module where they should be implemented.
Change their name using
asto prevent name collisions (example).
- Implement the traits next to their non-alpha versions (example).
While none of this is hard, some HAL maintainers might prefer not to add a dependency on an alpha version.
The main drawback of this approach is that it requires ongoing updates, as new
embedded-hal alpha versions come out.
As stated before,
-alpha versions are not guaranteed to be compatible with each other.
Minimum Supported Rust Version (MSRV)
This crate is guaranteed to compile on stable Rust 1.35 and up. It might compile with older versions but that may change in any new patch release.
Licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.